The invention relates to networked intelligent electronic devices and more particularly to a multiple communications port unit for coupling plural intelligent electronic devices to a computer over a network connection.
Protective relays are commonly used to protect electrical power distribution systems. In a simple form, a protective relay can be an electromechanical contact relay having an energizing circuit coupled to the load on an electric power distribution line. When the load exceeds certain parameters, the relay is energized to operate a circuit breaker, or the like, coupled to the line to thereby isolate a portion of the electrical distribution system having the fault. The contacts of the relay can perform various functions such as tripping a circuit breaker, generating an alarm or providing a signal to another protective relay. For the most part, such simple relays only provide the contact operation as an output. They do not provide an indication of the conditions which produced activity in the output contacts.
For instance, the principal of operation of a distance measuring relay is that the distance of a fault can be determined by a comparison of the complex impedance of the line derived from the current and voltage at the relay to a reach characteristic. If this comparison indicates that there is a fault within the protection zone of the relay, a trip contact is actuated. However, simple protective relays do not provide as an output any indication of where the fault is located or what the impedance was, or even what the current and voltage were which caused the trip. Similarly, a simple overcurrent relay trips in response to detection of a line current which exceeds a set point value, but it does not provide a quantitative indication of the magnitude of current which caused the trip.
Accordingly, xe2x80x9cintelligentxe2x80x9d protective relays have been developed having microprocessors capable of evaluating complex impedance or other variables to protect the electrical distribution system by isolating faults and capable of transmitting diagnostic data and the like to other computers for evaluation and display purposes. Typically, substations in an electric power system have many intelligent protective relays and other intelligent electronic devices (IED). The phrase intelligent electronic device, as used herein, refers to any distributed device having a microprocessor and being capable of carrying out control functions. Intelligent relays can be programmed to perform various protection functions. For instance, digital distance relays and overcurrent relays are in use. These relays are capable of providing a great deal of information. For instance, the location of the fault, and the current and voltage at the fault are available as outputs of a microcomputer controlled intelligent distance relay. Similarly, the current information is available from an intelligent overcurrent relay. This information generally is transmitted to a remote computer over separate RS-232 or RS 485 channels, i.e., serial channels, for each relay.
Accordingly, multiple serial port units have been developed. Such units include multiple serial ports, 8 or 16 for example, and an Ethernet port. The Ethernet port is coupled to a remote computer using standard Ethernet cable, for example an unshielded twisted pair (UTP), and protocols. The serial ports are each connected to an intelligent protective relay or other intelligent electronic device. The expansion unit uses known hardware and software to map the serial ports over the Ethernet connection to appear as local serial ports to the computer. Accordingly plural intelligent protective relays can be coupled to a computer over a great distance by a single Ethernet cable.
However, known multiple serial port units are powered by 120V/240 Vac or low voltage dc, e.g. 5V, 12V, 24V, or 48 Vdc. These voltages are not readily available in electrical distribution substation environments. In particular, electrical power at a substation is provided by the xe2x80x9csubstation batteryxe2x80x9d which is generally an 88-300 Vdc power supply. Therefore, various supplemental power transformers and converters must be used to convert the electric power available from the substation battery to electric power useable by multiple serial port units. Such supplemental transformers and converters introduce additional sources of failure in harsh substation environments. Further, the harsh substation environment often causes power supply failure. Also, electrical Ethernet links are susceptible to error in a high EMF area such as substations. For these reasons, it has been difficult to apply multiple serial port units in substation environments in a reliable manner.
A first aspect of the invention is a multiple communications port unit comprising plural communications ports adapted to be coupled to peripheral devices, a network port adapted to communicate with a computer over a network link, and a power supply unit coupled to the communications ports and to the network port and having an input voltage of greater than or equal to 88 Vdc.
A second aspect of the invention is a multiple communications port unit comprising plural communications ports adapted to be coupled to intelligent electronic devices, a fiber optic network port adapted to communicate with a computer over a network link, a power supply unit coupled to the communications ports and to the network port and having an input voltage of greater than or equal to 88 Vdc. The power supply unit includes two power supplies configured to operate in a redundant manner.
A third aspect of the invention is a computer architecture comprising a computer, plural peripheral devices, and a multiple port communications unit having plural communications ports coupled to the peripheral devices, a fiber optic network port coupled to the computer over a network link, and a power supply unit coupled to the communications ports and to the network port and having an input voltage of greater than or equal to 88 Vdc. The power supply unit includes two power supplies configured to operate in a redundant manner.
A fourth aspect of the invention is a multiple communications port unit comprising communication means for coupling the port unit to peripheral devices, network means for communicating with a computer over a network link and power supply means for providing power to the communication means and the network means. The power supply means has an input voltage of greater than or equal to 88 Vdc.